What scenarios are generally used for coaxial cables

Test voltage ripple with coaxial cable instead of general oscilloscope probe: because their accuracy is not the same, the general oscilloscope is not equipped with coaxial cable, because the general oscilloscope itself clip and ground wire will form a loop, like an antenna to receive noise, introducing some unnecessary noise, so many people use coaxial cable to test, in parallel should be two capacitors, one 10uf and one 104.

1. What is ripple?

Ripple is defined as the AC component superimposed on a DC stable amount of DC voltage or current.

It mainly has the following harms: it is easy to produce harmonics on electrical appliances, and harmonics will produce more harm; Reduced efficiency of the power supply; Strong ripples can cause surge voltages or currents, resulting in the burning of electrical appliances; It will interfere with the logical relationship of digital circuits and affect their normal operation; It will cause noise interference, so that the image equipment and audio equipment cannot work normally.

2. Ripple and ripple coefficient representation.

It can be expressed as a valid value or a peak, or as an absolute or relative quantity;

The unit is usually mv

For example, if a power supply works in a regulated state, its output is 12V5A, and the effective value of the measured ripple is 10mV, which is the absolute amount of ripple, and the relative quantity, that is, the ripple coefficient = ripple voltage Output current = 10mV 12V=.

3. Test method of ripple.

Take the bandwidth of the 20m oscilloscope as the limiting standard, set the voltage to PK-PK (there are also effective values), remove the clamp and ground wire on the oscilloscope control head (because this clip and ground wire will form a loop, like an antenna to receive noise, introducing some unnecessary noise), use the grounding ring (you can also use the grounding ring, but consider the error it generates), connect a 10UF electrolytic capacitor and a ceramic capacitor in parallel on the probe, and test directly with the probe of the oscilloscope; If the oscilloscope probe is not in direct contact with the output point, it should be measured with a twisted pair or 50 coaxial cable.

1. Bare wires and bare conductor products The main characteristics of this type of products are: pure conductor metal, no insulation and sheath layer, such as steel core aluminum stranded wire, copper-aluminum busbar, electric locomotive line, etc.; The processing technology is mainly pressure processing, such as smelting, calendering, drawing, stranding, pressing and stranding, etc.; The products are mainly used in suburbs, rural areas, user mainlines, switch cabinets, etc. 2. The main characteristics of this type of product are:

Extrude (wrap) the insulating layer outside the conductor, such as overhead insulated cables, or several cores stranded (corresponding to the phase wire, neutral wire and ground wire of the power system), such as overhead insulated cables with more than two cores, or add a sheath layer, such as plastic rubber sheathed wires and cables. The main process technologies are drawing, stranding, insulation extrusion (wrapping), cable formation, armoring, sheath extrusion, etc., and the different process combinations of various products are different. The products are mainly used in the transmission of strong electric energy in the power generation, distribution, transmission, transformation and power supply lines, with large current (tens of amperes to thousands of amperes) and high voltage (220V to 500kV and above).

3. Wires and cables for electrical equipment The main characteristics of this type of products are: a wide variety of specifications, a wide range of applications, the use of voltage in 1kV and below, in the face of special occasions continue to derive new products, such as fire-resistant cables, flame-retardant cables, low-smoke halogen-free low-smoke and low-halogen cables, termite-proof, anti-rat cables, oil-resistant, cold-resistant, temperature-resistant, wear-resistant cables, medical, agricultural mining cables, thin-walled wires, etc. 4. Communication cable and optical fiber (brief introduction) With the rapid development of the communication industry in the past 20 years, the products have also developed at an astonishing speed.

From the simple telegraph cable in the past, it has developed into thousands of pairs of telephone cables, coaxial cables, optical cables, data cables, and even combined communication cables. The structural size of this type of product is usually small and uniform, and the manufacturing accuracy is high. 5. Magnet wire (winding wire).

Coaxial cable refers to a cable with two concentric conductors, and the conductor and shield share the same axis. The most common coaxial cable consists of a copper wire silver conductor isolated by insulating material, another layer of annular conductor and its insulator on the outside of the inner layer of insulation, and then the entire cable is encased by a sheath of polyvinyl chloride or Teflon material.

Coaxial cables can be used for the transmission of analog and digital signals and are suitable for a wide variety of applications, the most important of which are television transmission, long-distance transmission**, short-distance connections between computer systems, and local area networks. Coaxial cable has developed rapidly as a means of transmitting TV signals to thousands of households, which is cable television. A cable TV system can load dozens or even hundreds of electric channels, and its propagation range can reach tens of kilometers.

For a long time, coaxial cables have been an important part of long-distance networks. Today, it faces increasing competition from fiber optics, terrestrial microwaves, and satellites.

1. The volume is large, and the diameter of the thin cable is 3 8 inches thick, which takes up a lot of space for the cable pipeline;

2. It cannot withstand entanglement, pressure and serious bending, which will damage the cable structure and prevent the transmission of signals;

3. The cost is high, and all these shortcomings can be overcome by twisted pairs, so in the current Qing cautious LAN environment, it has basically been replaced by the Ethernet physical layer specification based on twisted pairs.

What is Coaxial Cable? The basic unit (coaxial pair) is formed by two coaxial, mutually insulated cylindrical metal conductors, and then the cable is composed of one or more coaxial pairs.

Coaxial cable is a kind of communication cable, the cable structure is covered with a layer of insulating material with a solid copper body as the core, this layer of insulating material is surrounded by a densely woven mesh conductor, and the outside of the network is covered with a layer of protective material, there are two kinds of widely used coaxial cables, one by one for 50 ohm cable, for digital transmission, because it is mostly used for baseband transmission, it is also known as baseband coaxial cable; The other is a 75 ohm cable for analog transmission. Coaxial cables can support very wide bandwidth and have excellent noise rejection characteristics, so they can transmit data, voice and video at the same time.

A coaxial cable is a cable that has two concentric conductors, and the conductor and mask layer share the same axis. The most common coaxial cable consists of a copper wire conductor isolated by an insulating material, another ring conductor and its insulator on the outside of the inner insulation, and then the entire cable is encased by a sheath of PVC or Teflon material. [working principle of coaxial cable].

The coaxial cable is divided into four layers from the inside to the outside: the central copper wire (a single strand of solid wire or a multi-strand stranded wire), a plastic insulator, a mesh conductive layer and a wire sheath. The central copper wire and the mesh conductive layer form a current loop.

It is named because the central copper wire and the mesh conductive layer are coaxial. Coaxial cables conduct alternating current instead of direct current, which means that the direction of the current is reversed several times per second.

If a high-frequency current is transmitted using a normal wire, the wire acts as an antenna that emits radio outwards, an effect that dissipates the power of the signal and reduces the strength of the received signal.

Coaxial cables are designed to solve this problem. The radio emitted by the central wire is isolated by a mesh conductive layer, which can control the transmitted radio by grounding.

The structure of the coaxial cable].

The outer conductor of the coaxial cable has a dual role, it acts as a wire of the transmission loop, and has a masking effect, and the outer conductor usually has 3 structures.

1) Metal tubular form. This structure is welded with copper or aluminum strip longitudinal wrapping, or seamless copper tube extrusion and drawing, this structure form has the best masking performance, but the flexibility is poor, and it is often used for trunk cables.

2) Aluminum-plastic composite belt longitudinal package lap. This structure has a good masking effect and low manufacturing cost, but because the outer conductor is a round tube with a longitudinal slit, electromagnetic waves will leak through the gap, so it should be used with caution.

3) Combination of woven mesh and aluminum-plastic composite belt longitudinal bag. This is developed from a single woven mesh structure, it has the characteristics of good flexibility, light weight and reliable joints, experiments have proved that the use of reasonable composite structure, the performance of the mask is greatly improved, and this structural form is widely used at present.

Through the understanding of the above knowledge, what other issues do you think deserve our attention? Hopefully, this knowledge of coaxial cables will help you.

A coaxial cable is a cable composed of two coaxial and mutually insulated cylindrical metal conductors (coaxial pairs), and then composed of single or multiple coaxial pairs.

This kind of cable is generally used by enterprise construction sites, about the parameters of coaxial cables ** You can search for the effect of the purchase, the above information about industrial products is very accurate, it is recommended that you search.

Categories: Computer Internet >> Internet.

Analysis: There are two main types of coaxial cables, coarse coaxial cable and thin coaxial cable, and the sensitive coaxial cable is the longest transmission distance in the copper medium, and the transmission distance can reach 500 meters in the 10base5 standard. Thin coaxial cables can transmit up to 185 meters in the 10base2 standard.

At present, the application of coaxial cable in the computer network has been very little, and the supporting connection equipment is less and less, the main reason is that its production process is much more complex than that of twisted pair, and in the computer network of bus topology structure, all computer machines are connected in series on a medium, and any point out or the problem may cause the paralysis of the whole network. Therefore, copper axis cables are basically only used in cable TV networks, and the cable TV cables we usually see are thin coaxial cables.

Coaxial cable (coaxiai cable) is the most commonly used transmission medium in the network, there are four layers, the innermost layer is the central conductor, from the inside to the outside, it is divided into insulation, conductor network and protective sleeve, according to the bandwidth and use, coaxial cable can be divided into baseband (baseband) and broadband (broadband). The baseband coaxial cable transmits a digital signal, and during the transmission process, the signal will occupy the entire channel, and the digital signal includes the highest frequency that can be transmitted from 0 to the baseband coaxial cable, so that at the same time, the baseband coaxial cable can only transmit one signal. Wideband coaxial cables transmit signals of different frequencies that need to be modulated to different sinusoidal carrier frequencies by modulation techniques.

Frequency division multiplexing technology is used to divide into multiple channels for transmission, so that signals such as data, sound and image are transmitted in different channels at the same time. The performance of broadband coaxial cable is better than that of baseband coaxial cable, but it requires additional signal processing equipment, and it is more difficult to install, which is suitable for long-distance ** network, cable TV system and broadband computer network.

Answer: A coaxial cable consists of a hollow outer cylindrical conductor and an inner conductor located on the central axis. The inner conductor is separated from the cylindrical conductor and the outside by an insulating material. According to the different transmission frequency bands, coaxial cables can be divided into two types: baseband coaxial cable and broadband coaxial cable.

According to the different diameters, coaxial cables can be divided into thick cables and thin cables. Thin cables have developed rapidly in recent years, so thin cables are generally used in computer LANs if there are no special requirements. Thin cables are generally used for bus-type network cabling connections.

Use the T-type BNC connector to connect the BNC interface NIC, and install terminal resistors at both ends. The maximum length of each trunk of the thin cable network is 185 meters, and each trunk can access up to 30 users. If you want to widen the network range, you need to use repeaters, such as using 4 repeaters to connect 5 network segments, so that the maximum distance of the network reaches 925 meters.

The thin cable is easy to install, and the cost is low, but due to the limitation of the network wiring structure, its daily maintenance is not very convenient, once a user fails, it will affect the normal work of other users. The thick cable is suitable for the network trunk of the larger LAN, with a long wiring distance and good reliability. Users typically use an external transceiver to connect to the network trunk.

The length of each segment in the thick cable LAN can be up to 500 meters, and the maximum length of each segment can be up to 2,500 meters when five segments are connected by four repeaters. If the network is directly connected to the NIC with a thick cable, the NIC must have an AUI interface (15-pin D-type connector). Although the LAN is built with thick cables, although the performance is high and the transmission distance is large, the network installation and maintenance are more difficult and the cost is higher.

Select the cable model. The term cable can be a bit confusing. Look at the casing of the cable, which usually has instructions about the good fortune of the cable.

In the family, the most commonly used sizes are RG-6 and RG-59. RG stands for "Radio Guide". The numbers represent the diameter and inner diameter of the wire (59 means, and 6 represents the thinness of the shell and cable, which represents how much signal is lost per unit length.

You'll also see the word RF on the cable, which stands for "Radio Frequency". Although the thinner and lower standard RG-59 is still used in some older houses, the RG-6 is best known for most non-industrial coaxial cables. Commercial installers will use thinner RG cables, such as the RG-11 (which only works when the source is more than 200 feet away from your home's terminal).

RG cables for general purpose for household use should be 75OHM (RG-6 or RG-59). Note that all cables (and their connectors) have different qualities. Choose the best quality.